bit_alloc
, bit_clear
,
bit_count
, bit_decl
,
bit_ffc
, bit_ffs
,
bit_ffc_at
, bit_ffs_at
,
bit_ffc_area
, bit_ffs_area
,
bit_ffc_area_at
,
bit_ffs_area_at
, bit_nclear
,
bit_nset
, bit_set
,
bit_test
, bitstr_size
—
bit-string manipulation functions and macros
#include <bitstring.h>
bitstr_t *
bit_alloc
(int
nbits);
void
bit_decl
(bitstr_t
*name, int
nbits);
void
bit_clear
(bitstr_t
*name, int
bit);
void
bit_count
(bitstr_t
*name, int count,
int nbits,
int *value);
void
bit_ffc
(bitstr_t
*name, int nbits,
int *value);
void
bit_ffs
(bitstr_t
*name, int nbits,
int *value);
void
bit_ffc_at
(bitstr_t
*name, int start,
int nbits,
int *value);
void
bit_ffs_at
(bitstr_t
*name, int start,
int nbits,
int *value);
void
bit_ffc_area
(bitstr_t
*name, int nbits,
int size,
int *value);
void
bit_ffs_area
(bitstr_t
*name, int nbits,
int size,
int *value);
void
bit_ffc_area_at
(bitstr_t
*name, int start,
int nbits,
int size,
int *value);
void
bit_ffs_area_at
(bitstr_t
*name, int start,
int nbits,
int size,
int *value);
bit_foreach
(bitstr_t
*name, int nbits,
int var);
bit_foreach_at
(bitstr_t
*name, int start,
int nbits,
int var);
bit_foreach_unset
(bitstr_t
*name, int nbits,
int var);
bit_foreach_unset_at
(bitstr_t
*name, int start,
int nbits,
int var);
void
bit_nclear
(bitstr_t
*name, int start,
int stop);
void
bit_nset
(bitstr_t
*name, int start,
int stop);
void
bit_set
(bitstr_t
*name, int
bit);
int
bitstr_size
(int
nbits);
int
bit_test
(bitstr_t
*name, int
bit);
These macros operate on strings of bits.
The function bit_alloc
() returns a pointer
of type “bitstr_t *” to sufficient space
to store nbits bits, or NULL
if no space is available. If successful, the returned bit string is
initialized with all bits cleared.
The macro bit_decl
() declares a bit string
with sufficient space to store nbits bits.
bit_decl
() may be used to include statically sized
bit strings in structure definitions or to create bit strings on the stack.
Users of this macro are responsible for initialization of the bit string,
typically via a global initialization of the containing struct or use of the
bit_nset
() or bin_nclear
()
functions.
The macro bitstr_size
() returns the number
of bytes necessary to store nbits bits. This is useful
for copying bit strings.
The functions bit_clear
() and
bit_set
() clear or set the zero-based numbered bit
bit, in the bit string name.
The bit_nset
() and
bit_nclear
() functions set or clear the zero-based
numbered bits from start through
stop in the bit string name.
The bit_test
() function evaluates to
non-zero if the zero-based numbered bit bit of bit
string name is set, and zero otherwise.
The function bit_ffc
() stores in the
location referenced by value the zero-based number of
the first bit not set in the array of nbits bits
referenced by name. If all bits are set, the location
referenced by value is set to -1.
The bit_ffs
() function stores in the
location referenced by value the zero-based number of
the first bit set in the array of nbits bits
referenced by name. If no bits are set, the location
referenced by value is set to -1.
The function bit_ffc_at
() stores in the
location referenced by value the zero-based number of
the first bit not set in the array of nbits bits
referenced by name, at or after the zero-based bit
index start. If all bits at or after
start are set, the location referenced by
value is set to -1.
The bit_ffs_at
() function stores in the
location referenced by value the zero-based number of
the first bit set in the array of nbits bits
referenced by name, at or after the zero-based bit
index start. If no bits are set after
start, the location referenced by
value is set to -1.
The bit_ffc_area
() function stores in the
location referenced by value the zero-based number of
the first bit beginning a sequence of unset bits of at least
size unset bits in the array of
nbits bits referenced by name.
If no sequence of contiguous unset bits of the specified
size can be found, the location referenced by
value is set to -1.
The bit_ffs_area
() function stores in the
location referenced by value the zero-based number of
the first bit beginning a sequence of set bits of at least
size set bits in the array of
nbits bits referenced by name.
If no sequence of contiguous set bits of the specified
size can be found, the location referenced by
value is set to -1.
The bit_ffc_area_at
() function stores in
the location referenced by value the zero-based number
of the first bit beginning a sequence of unset bits of at least
size unset bits in the array of
nbits bits referenced by name,
at or after the zero-based bit index start. If no
sequence of contiguous unset bits of the specified
size can be found at or after
start, the location referenced by
value is set to -1.
The bit_ffs_area_at
() function stores in
the location referenced by value the zero-based number
of the first bit beginning a sequence of set bits of at least
size set bits in the array of
nbits bits referenced by name,
at or after the zero-based bit index start. If no
sequence of contiguous set bits of the specified size
can be found at or after start, the location
referenced by value is set to -1.
The bit_count
() function stores in the
location referenced by value the number of bits set in
the array of nbits bits referenced by
name, at or after the zero-based bit index
start.
The macro bit_foreach
() traverses all set
bits in the array of nbits referenced by
name in the forward direction, assigning each location
in turn to var.
The macro bit_foreach_at
() traverses all
set bits in the array of nbits referenced by
name in the forward direction at or after the
zero-based bit index start, assigning each location in
turn to var.
The macro bit_foreach_unset
() traverses
all unset bits in the array of nbits referenced by
name in the forward direction, assigning each location
in turn to var.
The macro bit_foreach_unset_at
() traverses
all unset bits in the array of nbits referenced by
name in the forward direction at or after the
zero-based bit index start, assigning each location in
turn to var.
The arguments in bit string macros are evaluated only once and may
safely have side effects.
#include <limits.h>
#include <bitstring.h>
...
#define LPR_BUSY_BIT 0
#define LPR_FORMAT_BIT 1
#define LPR_DOWNLOAD_BIT 2
...
#define LPR_AVAILABLE_BIT 9
#define LPR_MAX_BITS 10
make_lpr_available()
{
bitstr_t bit_decl(bitlist, LPR_MAX_BITS);
...
bit_nclear(bitlist, 0, LPR_MAX_BITS - 1);
...
if (!bit_test(bitlist, LPR_BUSY_BIT)) {
bit_clear(bitlist, LPR_FORMAT_BIT);
bit_clear(bitlist, LPR_DOWNLOAD_BIT);
bit_set(bitlist, LPR_AVAILABLE_BIT);
}
}
The bitstring
functions first appeared in
4.4BSD.